The present invention relates to a remote controller, for use in electric or electronic appliances and telecommunication devices such as television sets. More particularly, the present invention relates to an electronic circuit for a remote controller receiver unit which is capable of controlling operations of a television receiving set such as turning on or off of a main switch, switching-over of a tuner unit for channel selection or turning a volume control for loudness adjustments.
Conventionally, in the remote controller of the above described type, the receiver usually includes, as shown in FIG. 1, a microphone for receiving sound signal of high frequency, for example ultra-sonic waves of approximately 20 KHz from a transmitter, and for converting such sound signal into electrical signal, an amplifier for amplifying the electrical signal, and a frequency modulation detector (referred to as FM detector hereinbelow) for detecting particular FM signal. The detected signal is generally distributed into numbers of series networks for operating particular tuning devices coupled to respective series networks by an operator circuit connected at the end of each series network. The tuning devices to be operated are, for example, device for turning on the television set, device for changing the volume of the loudness, device for switching-over the channel in the television set, etc. In the known arrangement of FIG. 1, the detected signal is distributed into two channels, in which the first channel is capable for receiving electrical signal in particular frequency such as 380 Hz, and the second channel is capable for receiving electrical signal in another particular frequency such as 280 Hz. The first channel includes a filter for filtering the signal having the frequency of 380 Hz, a relay driver for actuating a relay connected to the relay driver upon receipt of the signal from the filter, the relay, and the operator which operates the particular device coupled thereto.
The arrangement for the second channel is similar to those for the first channel, but the difference is that the filter in the second channel is designed to filter the signal having the frequency of 280 Hz.
In order to operate the receiver, the one who operates must have his transmitter aimed at the receiver, especially at the microphone, during the emission of sound signals in high frequency from the transmitter.
However, it has been found that the sound signal produced from the transmitter may deteriorate the operation of the receiver when the properly aimed sound signal changes the course to deviate from the microphone, or when the deviated sound signal changes the course to come into properly aimed position due to shaking or moving around the transmitter by the one who operates during the manipulation thereof.
Such change in the course causes fluctuations in the amplitude of the received sound signal in the microphone and in turn results in fluctuations in the input electrical signal to the FM detector, so that the FM detector may not function properly, especially when the input electrical signal is decreased below the limit level for the FM detector, to produce the proper electrical signal therefrom. Therefore, the transistors incorporated in the relay driver may fail to function in a proper manner, such that the signal produced from the relay driver may cause fluctuations in the operation of the transistors quite rapidly between conducted and non-conducted state, thus resulting in the undesirable intermittent closure of open contacts or opening of closed contacts in the relay, i.e., the so-called relay contact chattering.